The outcome of a bitter struggle in the streets of the capital could affect the balance of power in the wider region

SOON after last summer's war brought ruin to Lebanon, a clever advertising campaign helped boost morale. “Keep Walking”, said billboards for Johnnie Walker whisky that showed the eponymous dandy in his riding coat striding along, next to the silhouette of a fallen bridge. A new, updated version carries the same jaunty caption, but the overcome obstacle is an intricate maze. The hopeful reference is to Lebanon's own Byzantine politics. But unlike the dauntless Mr Walker, Lebanon is not moving. It is stuck.

Talks between faction leaders, aimed at bringing the opposition into a unity government and soothing tensions raised by the war, collapsed last month. Since then, fractures between religious sects, divided political loyalties and clashing understandings of Lebanon's own history and identity have widened dangerously fast.

The polarisation is being graphically enacted in central Beirut. Opposition protesters have erected a festive city of 600 tents (many of them donated by relief agencies for war refugees) below the Saray, an Ottoman-era barracks that serves as the office of the embattled prime minister, Fouad Siniora. Huge crowds gather nightly to chant for his downfall, even as he receives endless delegations of supportive dignitaries. Elsewhere amid the city's sectarian patchwork, the presence of some 20,000 army troops has not stopped brawls from breaking out between pro- and anti-government gangs. One person has been killed so far; expect more deaths.

The showdown, which has brought Lebanon's economy to almost as complete a halt as the recent war, shows no sign of ending soon. The protesters claim to represent most of Lebanon's 5m people, and certainly are backed by the vast bulk of its 30% Shia minority as well as disgruntled Christians, pro-Syrian factions, communists and others. They charge Mr Siniora with corruption, incompetence and submissiveness to Western powers, and say that last month's resignation of Shia ministers rendered the government illegal, since the constitution says that cabinets should fairly represent every sect. They insist that their vigil will not end until the prime minister, who must by law be a Sunni Muslim, appoints enough opposition ministers to grant them an effective veto over policy.

Mr Siniora's government, several of whose members have feared leaving the Saray since last month's assassination of their fellow minister, Pierre Gemayel, scion of a leading Christian clan, has offered the opposition a bigger share of posts. But it remains adamant that this must fall short of a veto quota: that would fly in the face of the parliamentary majority won by the anti-Syrian coalition in an election after Syrian forces, once overlords, left Lebanon in high dudgeon last year.

This week, Mr Siniora was said to have accepted a proposal to up the number of cabinet posts from 24 to 30, giving nine or ten to the Hizbullah-led opposition, 19 to the anti-Syrian coalition and a couple to neutrals. Not enough, said Hizbullah. Mr Siniora's lot say they will accept a unity government on several conditions. Parliament, they say, must give the go-ahead for a tribunal to look into the murder of Rafik Hariri, the five-times prime minister killed by a car bomb in February 2005. Also, there must be an early presidential election; the current president, Emile Lahoud, is a pro-Syrian Christian whose term was controversially extended in 2004.

In the government's view, the demonstrations are subverting democracy. Their aim, it asserts, is not so much to achieve a sectarian balance as to bring Lebanon back into the orbit of Syria and its ally, Iran, so as to renew “resistance” against their mutual enemy, Israel. Hence the opposition's determination to block approval of an international tribunal to try suspects in the murder of Lebanese critics of Syria. The government also says the opposition wants to scale back Lebanese co-operation in keeping peace on the border with Israel, where a 10,000-man UN force patrols alongside the Lebanese army.

“We are here to implement democracy,” says Saad Hariri, a Sunni strongman and political heir to his murdered father. “They are here to implement a 22-year-old Iranian project.” Nawaf Musawi, Hizbullah's foreign-affairs chief, counters that it is the government's acceptance of UN troops and foreign aid that is whittling away Lebanese sovereignty. “They're taking us back to the status of a mandatory state,” he asserts.

On the ground, the opposition appears stronger. The demonstration that began their protests brought out more than 1m enthusiasts, a gathering at least as big as those in last year's Cedar Revolution against Syrian tutelage. Hizbullah, the Iranian-financed and Syrian-equipped Shia party that fought Israel, lends the opposition formidable organising skill as well as the quiet menace of its unrivalled guerrilla force. Ceaseless propaganda beams from opposition radio and television stations, such as Hizbullah's Al-Manar.

But Mr Siniora is not bereft of resources. Aside from Western powers and Sunni Arab allies such as Saudi Arabia, he enjoys strong support from anti-Syrian Christian factions; he also has near-unanimous backing from the Sunni and Druze minorities, who make up about 30% and 6% respectively of Lebanon's people. The pro-government media blast out plenty of countering tirades.

In fact, there is a striking symmetry between the two sides. Each accuses the other of being the stooge of foreign powers, of stoking sectarian rivalry and of “trading in the blood of martyrs”. Whereas the government used the killing of Mr Gemayel to rally its supporters, Hizbullah fanned opposition fury by wheeling the flag-draped coffin of a shot Shia youth into the downtown protest, amid televised cries of “Death to Siniora!” Both sides claim majority backing, and both see the clash as a defining moment for Lebanon—perhaps even for the wider region. Neither is in a mood to give in.

How will it end? No one is sure, though the momentum seems to be with Hizbullah. The West, especially the Americans but also the European Union, are keen to keep Mr Siniora going. Conservative Arab governments, especially in Egypt, Jordan and Saudi Arabia, are worried. If Mr Siniora is forced out of office at Hizbullah's insistence, angry Sunni Arab fears of a new “Shia arc” stretching from Lebanon across to Iraq and on to Iran—the image gloomily aired last year by Jordan's King Abdullah—will grow.